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Table 3 Eligible PICO/PECO (I/E: Intervention or Exposure) and study types

From: How effective are strategies to control the dissemination of antibiotic resistance in the environment? A systematic review

S1. Restriction of antibiotic use S2. Treatments of liquid and solid matrices S3. Natural environment management
Eligible populations
Any human, animal (domestic, livestock, aquaculture) or plant susceptible to receive antibiotics as preventive or curative treatment Any matrix contaminated by ATBR and destined to a process:
Liquid matrices: e.g., wastewater, livestock slurry, waste milk (unsafe for consumption after antibiotic treatment), source of drinking water
Solid matrix: e.g., sewage sludge, livestock manure, any organic waste product
Any natural compartment contaminated by ATBR:
Aquatic environment: e.g., lake, river, coastal environment, sea
Terrestrial environment: e.g., agricultural soils, soils from natural parks
Eligible interventions (primary objective)
Any intervention to reduce the antibiotic use, e.g.:
Ban of antibiotics, particularly as growth promoters in husbandries
Alternative or preventive treatment (herbal medicines, essential oils, probiotics, prebiotics)
Optimization of the antibiotic use (doses and treatment duration)
Better hygiene conditions
Livestock management practices (free-range or organic farms)
Any process on matrices contaminated by ATBR, e.g.:
Primary (e.g., coagulation, flotation), secondary (e.g., activated sludge, membrane, ponds), tertiary treatments (e.g., advanced oxidation processes, nano/ultrafiltration, activated carbon) in wastewater or drinking water treatment plants
Aerobic or anaerobic digestion
Any environmental management option, e.g.:
Buffer zone
Frequency of organic waste spreading
Solutions to be identified
OR Eligible exposures (other objective)
To antibiotics as preventive or curative treatments To pollutants responsible for the selection or co-selection of resistance, e.g.: antibiotics, metals, biocides To sources of contamination by ATBR, e.g. discharge of the WWTP, organic waste spreading on agricultural soils, various municipal waste in landfills, aquaculture activities, agricultural and farming activities, urbanization and rejection of untreated wastewaters
Eligible comparators
Alone or in combination (e.g., BACI for before/after/control/intervention): Before I/E, Control or Comparator without I/E, comparator with another I/E
Absence of comparator led to exclusion of the article
Eligible outcomes for ATBR in environment
ATBR defined as:
Antibiotic resistant bacteria (ARB) measured through culture-based methods:
 Concentration or absolute abundance, e.g., in colony forming unit (CFU) per volume or mass of sample
 Proportion or relative abundance in % resistant isolates in the measured bacterial population (e.g., total culturable bacteria, total Escherichia coli isolates)
Antibiotic resistance genes (ARG) and mobile genetic elements (MGE) measured through molecular methods:
 Concentration or absolute abundance in gene copies per volume or mass of samples
 Proportion or relative abundance in gene copies per total microbial biomass, e.g., estimated by the 16S sub-unit of ribosomal ribonucleic acid (16S rRNA genes copies)
Concentrations/Absolute abundances were used for risk assessment associated to the presence of ARB, ARG and MGE
Proportions/Relative abundances were used for quantitative comparisons since the I/E can also impact the total microbial biomass and to overcome the difference between matrices
Environmental samples defined as liquid (e.g. wastewater) and solid matrices (e.g. sewage sludge, livestock manure), natural environment samples including water and sediment from aquatic environment, soil and biological samples from wildlife
Eligible study types
 Inclusion: laboratory-scale and field-scale environmental studies; modelling studies only if a dataset was acquired from experiments or observations
 Exclusion: clinical studies, pure simulation studies, reviews and opinion papers even if considered as potential secondary information sources